mingw_strbuf_realpath(): handle case of non existent last path component

git often requests `strbuf_realpath(path + "/.git")`, where "./git" does
not yet exist on disk.

This causes the following to happen:
1. `mingw_strbuf_realpath()` fails
2. Non-mingw `strbuf_realpath()` does the work
3. Result of `strbuf_realpath()` is slightly different, for example it
   will not normalize the case of disk/folder names
4. `needs_work_tree_config()` becomes confused by these differences
5. clone adds `core.worktree` setting

This in turn causes various problems, for example:
1. Repository folder can no longer be renamed/moved without breaking it
2. Using the repository on WSL (Windows Subsystem for Linux) doesn't
   work, because it has windows-style path saved

This fixes #2569

Signed-off-by: Alexandr Miloslavskiy <[email protected]>

Author: SyntevoAlex

compat/mingw.c

@@ -1287,35 +1287,63 @@ struct tm *localtime_r(const time_t *timep, struct tm *result)
 	return NULL;
 }
 
-char *mingw_strbuf_realpath(struct strbuf *resolved, const char *path)
+static int realpath_existing_file(struct strbuf *resolved, const char *path, int path_len)
 {
 	wchar_t wpath[MAX_PATH];
 	HANDLE h;
 	DWORD ret;
 	int len;
 
-	if (xutftowcs_path(wpath, path) < 0)
-		return NULL;
+	if (xutftowcs_path_ex(wpath, path, MAX_PATH, path_len, MAX_PATH, 0) < 0)
+		return -1;
 
 	h = CreateFileW(wpath, 0,
 			FILE_SHARE_READ | FILE_SHARE_WRITE | FILE_SHARE_DELETE, NULL,
 			OPEN_EXISTING, FILE_FLAG_BACKUP_SEMANTICS, NULL);
 	if (h == INVALID_HANDLE_VALUE)
-		return NULL;
+		return -1;
 
 	ret = GetFinalPathNameByHandleW(h, wpath, ARRAY_SIZE(wpath), 0);
 	CloseHandle(h);
 	if (!ret || ret >= ARRAY_SIZE(wpath))
-		return NULL;
+		return -1;
 
 	len = wcslen(wpath) * 3;
 	strbuf_grow(resolved, len);
 	len = xwcstoutf(resolved->buf, normalize_ntpath(wpath), len);
 	if (len < 0)
-		return NULL;
+		return -1;
 	resolved->len = len;
-	return resolved->buf;
+	return 0;
+}
 
+char *mingw_strbuf_realpath(struct strbuf *resolved, const char *path)
+{
+	char *last_component;
+
+	if (realpath_existing_file(resolved, path, -1) >= 0)
+		return resolved->buf;
+
+	/*
+	 * strbuf_realpath() allows last path component to not exist.
+	 * Resolving full path failed, now it's time to try without last component.
+	 *
+	 * Retry on all errors to better match behavior of `strbuf_realpath()`.
+	 * For example, for no-access last directory, `strbuf_realpath()` ignores
+	 * that (because it doesn't try to `CreateFile()`) and still succeeds.
+	 */
+
+	last_component = find_last_dir_sep(path);
+	if (!last_component)
+		return NULL;
+
+	if (realpath_existing_file(resolved, path, last_component - path) < 0)
+		return NULL;
+
+	/* Force / instead of \ in appended component */
+	strbuf_addch(resolved, '/');
+	strbuf_addstr(resolved, last_component + 1);
+	return resolved->buf;
 }
 
 char *mingw_getcwd(char *pointer, int len)

t/t5601-clone.sh

@@ -68,6 +68,13 @@ test_expect_success 'clone respects GIT_WORK_TREE' '
 
 '
 
+test_expect_success CASE_INSENSITIVE_FS 'core.worktree is not added due to path case' '
+
+	mkdir UPPERCASE &&
+	git clone src "$(pwd)/uppercase" &&
+	test "unset" = "$(git -C UPPERCASE config --default unset core.worktree)"
+'
+
 test_expect_success 'clone from hooks' '
 
 	test_create_repo r0 &&